Secondary electron multiplier glass

ABSTRACT

A glass material for producing a secondary electron multiplying tube which comprises, in mol percent, V2O510 to 45, WO3 0 to 45, Fe2O3 0 to 25, WO3 + Fe2O3 15 to 45, BaO 0 to 15, PbO 0 to 15, P2O5 30 to 75 and SiO2 0 to 15.

United States Patent Asahara et al.

SECONDARY ELECTRON MULTIPLIER GLASS Inventors; Yoshiyuki Asahara, Kanagawa;

Tetsuro Izumitani, Hino, both of Japan Assignee: Hoya Glass Works, Ltd., Tokyo,

Japan Filed: Mar. 5, 1974 Appl. No.: 448,441

Foreign Application Priority Data Mar. 5, 1973 Japan 48-25822 [1.5. CI 106/53; 106/50; 106/47 R;

252/519, 252/521; 106/52 Int. Cl. C03C 3/00 Field of Search 106/47 R, 47 Q, 50, 52,

Primary ExaminerPatrick P Garvin Assistant Examiner-John F. Niebling Attorney, Agent, or FirmSughrue, Rothwell. Mion, Zinn & Macpeak [57] ABSTRACT A glass material for producing a secondary electron multiplying tube which comprises, in mol percent, V O 1O to 45, W0 0 to 45, Fe O 0 to 25, W0 Fe o 15 to 45, BaO O to 15, PbO 0 to 15, P 0 30 to 75 and S10 0 to 15.

3 Claims, 2 Drawing Figures TmW JIMI

SECONDARY ELECTRON MULTIPLIER GLASS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a glass suitable for a secondary electron multiplier having a secondary electron emission ratio 8 of more than 1 and a semiconducting property and capable of formation into tubes and fbers. 2. Description of the Prior Art A channel electron multiplier is produced by forming a material having a secondary electron emission ratio 8 of more than 1 into a tube or by arranging a pair of plates of this material in parallel with each other. Examples of channel electron multipliers are disclosed in J. Adams & B. W. Manley: IEEE Trans Nucl. Sci. NS-l3 (1966) 88, K. C. Schmidt and C. F. Handee: ibid NS-13 (i966) 100, C. A. Spindt and K. R. Shoulder: Rev. Sci. Instrurn, 36 (1965) 775, J. Dimeff, A. J. Lieber & C. N. Burrows: ibid, 37 (I966) 1562 and D. S. Evans: ibid, 36 (1965) 375.

When an electric voltage is applied to both ends of the channel electron multiplier, an electron entering one end (inlet end) of the channel collides with the inner wall generating one or more secondary electrons and is accelerated by the applied field towards the other end (outlet end). The multiplication of the secondary electrons is carried out by repeating such collisions. The tube shaped multiplier is a bundle of several hundred thousand extremely slender tubes and formed in a two dimentional plate. This is called the channel plate and is well known to be useful as an image intensifier, for example, as disclosed in J. Adams & B. W. Manley: Phillips Techn. Rev., 28 (I967) 156, W. C. Wiley & C. F. Hendee: IRE Trans Nucl. Sci. NS-9 (1962) 103, P. J. Turner et al: J. Sci. lnstrum., 2 (1969) 731, W. Parkes, R. Gott & K. A. Pounds: IEEE Trans Nucl. Sci. NS-l7 3 1970) 360 and R. Gott, w. Parkes and K. A. Pounds: ibid NS-l7, [3] (1970) 367 with applications thereof as in Electronics, Sept. 27, 1973 pl 17, Electra-Optical System Design, November, 1972 p29, Advance in Electronics and Electronphysics, 28A (1969) p471, Academic Press, London and New York. The material used for producing the secondary electron multiplier and the channel plate must have a 8 value of more than 1 and must be formed easily into the tube for exhibiting the above multiplying mechanism. Especially, the material for producing the channel plate must be formed easily into a slender tube (See G.A. Chuiko & A. M. Yakobson: Radio Engineering and Electronic Physics, ll (I966) 147]).

On the other hand, since a channel multiplier exhibiting the above multiplying machanism emits numerous secondary electrons at the outlet end (usually the electron introduced at the inlet end of the channel multiplier results in 10" electrons at the outlet), the inner wall surface near the outlet of the channel is positively charged. Accordingly, the linear property of the multiplied gain is lost and the channel is distorted at the outlet end of the applied voltage (i.e. the voltage for accelerating the electrons). The material for the multiplier must have an electron conducting property and a low electric resistance suitable for forming an electron supplying passage, i.e., a resistivity of less than 10 cm and larger than [0 (km.

Glass has been utilized for producing the secondary electron multiplying tube since glass is easily formed into a tube or fiber. Ordinary glass, however, exhibits too high a resistivity, i.e., about 10 Q-cm at room temperature, to produce an electron supplying passage. To solve this problem, a glass containing a large amount of PbO was usually heat-treated in a hydrogen gas atmosphere to form a layer of low resistance on the glass su rface. This low resistance surface layer, however, is influenced to a great extent by the heat treating conditions', thus a highly accurate technique is required for forming a stable and uniform surface layer of low resistance in the production of the PbO containing glass.

On the other hand, attempts have been made, e. g., as set forth in the above cited and in US. Pat. No. 3,520,831, to produce a stable and uniform multiplier tube material having a low resistance by using a semiconductor glass with the intention being to eliminate the above intricate techniques in glass production. However, a glass composition containing oxides of the transition elements, which is well known as a semiconductive glass, exhibits a low electric resistance but is difficult to draw into a tube or fiber. Especially, a glass composition containing V 0 exhibits an extremely low electric resistance (about 10 Q-cm) and is very stable, but exhibits a very low viscosity and can be drawn into a tube or fiber only with extreme difficulty. In addition, a glass containing oxides of other transition elements such as W0 or Fe O does not exhibit as low an electric resistance and is unstable, and is also difficult to draw into a tube or fiber.

SUMMARY OF THE INVENTION This invention is made on a discovery that a glass having a low electric resistance, good stability and a fully high viscosity suitable for drawing into a tube or fiber can be obtained by incorporating V 0 and (W0 and/or Fe O into the glass. Where the viscosity of the glass is intended to be elevated using compounds other than W0 and Fe O the amount of V 0 must be duly reduced thereby to reduce the low resistance; that is to say, WO and/or Fe O increases the viscosity and also retains a low resistance.

The secondary electron multiplying glass according to this invention consists, by mol percent, of V 0 10 to 45, W0 0 to 45, Fe O 0 to 25, W0 Fe O l5 to 45, BaO 0 to 15, PhD 0 to 15, P 0 30 to and SiO 0 to 15.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS FIG. 1 is a circuit for measuring the secondary electron emitting rate of the glass according to this invention.

FIG. 2 is a characteristic curve showing the relation between the applied voltage and the secondary electron emitting rate of the glass in Example 2.

DETAILED DESCRIPTION OF THE INVENTION If the amount of V 0 is less than 10 percent, the electric resistance of the glass cannot be reduced and the glass becomes unstable in the copresence of W0 and Fe O On the other hand, if the V 0 amount exceeds 45 percent, the resultant glass shows a low viscosity and cannot be drawn into a tube or fiber. However. the reduction of the V 0 content improves the forming property of the glass. It becomes possible when WO content is more than l5 mol percent. The following glass composition is preferable: V 0 l0 to 29.5 mol percent, W0 15 to 25 mol percent, BaO 10 to 15 mol percent, P 0 35 to 50 mol percent, SiO 5 to 15 3 mol percent.

More than 25 percent of Fe O and more than 45 percent of W cause the glass to be unstable.

If the sum of the Fe O amount and the W0,, amount is less than 15 percent, the resulting glass exhibits a low melting point, a low viscosity and a high electric resistance.

An amount of less than 30 percent of P 0 renders the glass unstable, whereas more than 75 percent of P 0 amount increases the electric resistance of the glass due to the relative reduction of the amount of the oxides of the transition elements.

We, the inventors, have also discovered that the viscosity of the V 0 4 W0 Fe O )-P O glass can be improved without increasing the electric resistance by introducing thereto BaO and PbO and/or by substituting a part of the P 0,- with SiO If the amounts of BaO and PbO exceed percent, the amounts of the oxides of the transition elements are reduced and the resulting glass shows a high resistance. When the PhD content is 5 to l5 mol percent, the amount of the V 0 can be reduced to mol percent and the forming property of the glass is improved. A glass composition as follows is especially preferable: V 0 l5 to 25 mol percent, W0 l5 to l7 mol percent, BaO 3 to 7 mol percent, PbO 5 to 15 mol percent, P 0 40 to 55 mol percent, SiO: 0 to l0 mol percent.

If more than 15 percent of P 0 is substituted with SiO the insoluble Si0 undesirably exists in the resulting glass.

Some examples of the glass of this invention will be shown in the following table to illustrate the invention in greater detail.

4 the applied voltage E which is obtained by the power battery in the circuit for measuring the secondary electron emitting rate in FIG. 1, on the 5m value, respectively.

in this measuring circuit, A is an emission source of the primary electron e, B is a sample of the glass according to this invention with which the primary electron collides, and C is a collector for the secondary electrons C emitted from the specimen B. By measuring an electric current C emitted from the specimen B. By measuring an electric current lp caused by the pri mary electron and an electric current is caused by the secondary electrons, a secondary electron emitting ratio 8(ls/lp) was obtained.

Curve (a) in FIG. 2 is an E- characteristic curve for the glass sample in Example 3.

As is particularly described above, the glass according to this invention exhibits a relatively low electric resistance, a 8 value of more than I, and a favorable property suitable for producing a secondary electron multiplier.

The plasticity and the workability of the glass of this invention were examined by an experiment wherein a glass tube having a diameter of 20 to 40 cm and made from the glass specimen in Example 5 could be drawn into the slender tube having the length of more than 1 The glass of this invention can be produced by mixing the components and melting the glass composition in a clay, silica or alumina crucible at l,200 to l,350C. More particularly, the glass of this invention can be produced by mixing the components, placing the mixture of the glass composition into a clay, silica or alu- Table l No. Composition (mol%) Secondary V,()5 W03 F620; 8210 PbO P205 SiO Electron Emitting Rate m) 1 30 20 50 L6 2 10 20 a 62 LI 3 20 40 5 2.25 4 20 50 5 10.6 37.6 14,2 37.5 6 I5 20 l5 50 7 IU 25 l5 so s 20 I5 l5 so q 20 I5 l5 s l0 20 I5 l5 40 I0 ll 20 I5 l5 3s 12 20 l5 5 I0 Table 2 mina crucible, heating at 1,200 to l,350C for about 9 to 10 hours in an air atmosphere, cooling to the trans- Xwfif formation temperature Tg and annealing. The cooling No Stu Is Electric Transition Softening process comprises two steps, i.e., a slow cooling in the 321:7? 3 :2 r i re earlier part of the cooling and a free cooling in air. During the earlier part of the cooling (from 1,200 g 2 1-32; 1 2 l,350C to about 900C), mixing is carried out in order 3 200 2.60 I0 550 592 to obtain homogenity. The slow cooling rate is about 2 2-33 :8: Z38 lOOC/hr. Annealing is carried out by holding the glass 6 X 550 600 near Tg for about ID to 12 hours, cooling to a tempera- 7 2.77 x 10" ture of 100C lower than Tg with the rate of cooling g I I 22: about --5C/hr, and free cooling in the furnace. 10 540 575 While this invention has been described with refer- :g i ence to specific embodiments thereof, it will be understood that the various changes and modifications can The 6m value and the Em value in the Tables show the maximum value 8 of the secondary electron emitting ratio and the maximum value (as shown in FIG. 2) of be made by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

5 2. The glass material according to claim 1 which con- A glass material for producmg a secondary elecsists, by mol percent, of V205 to 295 W03 '5 to tron multiplying tube which consists, by mol percent, of B30 l0 l0 2 5 35 P 50 2 3. The glass material according to claim I which con- V205 l0 45, 3 0 to 45, 2 3 0 a sists, by me] percent, of V 0 15 to 25, W0 15 to l7,

5 Fe O l5 m 45, BaO 0 m 15, PhD 0 to is, Phd 20,, 8 3 t0 Pbo 5 P105 50 to 55 and 2 0 and to 75 and SiO, 0 to 15. i w 

1. A GLASS MATERIAL FOR PRODUCING A SECONDARY ELECTRON MULTIPLYING TUBE WHICH CONSISTS, BY MOL PERCENT, OF V2O5 10 TO 45, WO30 TO 45, FE2030 TO 25,WO3+FE20315 TO 45, BAO O TO 15, PBO 0 TO 15, PHD 205 30 TO 75 AND SIO2 0 TO 15
 2. The glass material according to claim 1 which consists, by mol percent, of V2O5 10 to 29.5, WO3 15 to 25.0, BaO 10 to 15, P2O5 35 to 50 and SiO2 5 to
 15. 3. The glass material according to claim 1 which consists, by mol percent, of V2O5 15 to 25, WO3 15 to 17, BaO 3 to 7, PbO 5 to 15, P2O5 50 to 55 and SiO2 0 and
 10. 